Abstract:

A programmable thermostat has two way communication with a utility using a
power carrier line signal across distributed low voltage power lines in a
building downstream of an HVAC system transformer. The two way PLC
communication includes transmission to the utility of response
information regarding the response taken by the thermostat to a power
"shed" command, and preferably also includes sensed temperature and/or
temperature set point information. The HVAC system transformer includes
an integral capacitive bypass path for PLC data transmission across the
windings of the transformer. The thermostat positions its temperature
sensor to avoid heat given off by the PLC receiver/transmitter and its
electrical circuits as well as the thermostat microprocessor and the
electrical power circuits therefore.

Claims:

1. A distributed power line communicating thermostat control system
comprising:a HVAC system transformer adapted for lowering primary
alternating current power voltage within a building to secondary
alternating current power voltage for an HVAC system, the transformer
having a primary winding and a secondary winding;a capacitor electrically
connected across the primary winding and secondary winding of the HVAC
system transformer, the capacitor assisting in analog transference of a
power line communication radio frequency signal across the HVAC system
transformer;a programmable thermostat electrically connectable to the
HVAC system transformer for being powered by the secondary alternating
current power voltage at a distributed distance from the HVAC system
transformer; the programmable thermostat comprising:a power line
communication reception/transmission system for receiving the power line
communication radio frequency signal from the secondary alternating
current power voltage lines and for deriving control instructions from
the received power line communication radio frequency signal, and for
transmitting a radio frequency response signal onto the secondary
alternating current power voltage lines based upon response information;
anda control processor programmed to change thermostat functions based
upon control instructions from the power line communication reception
system, the control processor also programmed to provide response
information to the power line communication reception/transmission
system.

2. The distributed power line communicating thermostat control system of
claim 1, wherein the programmable thermostat further comprises:a
temperature sensor providing a sensed temperature value to the control
processor, wherein the temperature sensor, the control processor, power
circuits for the programmable thermostat and the power line communication
reception/transmission system are mounted in a housing, with the
temperature sensor positioned in the housing lower than the control
processor, the power circuits and the power line communication
reception/transmission system so as to sense ambient air temperature
while minimizing error introduced from heat generated by the control
processor, the power circuits and the power line communication
reception/transmission system.

3. The distributed power line communicating thermostat control system of
claim 1, wherein the programmable thermostat further comprises:a humidity
sensor providing a sensed humidity value to the control processor,
wherein the humidity sensor, the control processor, power circuits for
the programmable thermostat and the power line communication
reception/transmission system are mounted in a housing, with the humidity
sensor positioned in the housing lower than the control processor, the
power circuits and the power line communication reception/transmission
system so as to sense ambient air humidity while minimizing error
introduced from heat generated by the control processor, the power
circuits and the power line communication reception/transmission system.

4. The distributed power line communicating thermostat control system of
claim 1, wherein the programmable thermostat further comprises:an
occupancy sensor providing a sensed occupant result to the control
processor.

5. The distributed power line communicating thermostat control system of
claim 4, wherein the programmable thermostat transmits occupancy
information onto the secondary alternating current power voltage lines.

6. The distributed power line communicating thermostat control system of
claim 1, wherein the capacitor has a capacitance of 50 to 10000 pico
farads.

7. The distributed power line communicating thermostat control system of
claim 1, wherein the capacitor has a capacitance of 500 to 1000 pico
farads.

8. The distributed power line communicating thermostat control system of
claim 1, wherein the secondary alternating current power voltage is at 24
volts.

9. The distributed power line communicating thermostat control system of
claim 1, wherein the control instructions are Utility AMI instructions.

10. The distributed power line communicating thermostat control system of
claim 1, wherein the programmable thermostat provides one or more output
terminals for controlling HVAC equipment.

11. The distributed power line communicating thermostat control system of
claim 1, wherein the programmable thermostat provides one or more input
terminals for receiving HVAC information signals.

12. The distributed power line communicating thermostat control system of
claim 1, wherein the response information comprises actions taken by the
programmable thermostat in response to a shed condition provided in real
time by the programmable thermostat.

13. The distributed power line communicating thermostat control system of
claim 1, wherein the programmable thermostat transmits sensed temperature
information onto the secondary alternating current power voltage lines.

14. The distributed power line communicating thermostat control system of
claim 1, wherein the programmable thermostat transmits temperature set
point information onto the secondary alternating current power voltage
lines.

15. A power line communicating programmable thermostat comprising:a power
line communication reception/transmission system for receiving the power
line communication radio frequency signal on low voltage lines and for
deriving control instructions from the received power line communication
radio frequency signal, and for transmitting a radio frequency response
signal onto the secondary alternating current power voltage lines based
upon response information;a temperature sensor;an output for controlling
HVAC equipment;a control processor programmed to change thermostat
functions based upon sensed temperature and based upon control
instructions from the power line communication reception system, the
control processor also programmed to provide response information to the
power line communication reception/transmission system; andpower circuits
for the programmable thermostat, the power circuits operating on a HVAC
system voltage less than 120 volts, wherein the temperature sensor, the
control processor, power circuits for the programmable thermostat and the
power line communication reception/transmission system are mounted in a
housing, with the temperature sensor positioned in the housing lower than
the control processor, the power circuits and the power line
communication reception/transmission system so as to sense ambient air
temperature while minimizing error introduced from heat generated by the
control processor, the power circuits and the power line communication
reception/transmission system.

16. The power line communicating programmable thermostat of claim 15,
further comprising:a humidity sensor providing a sensed humidity value to
the control processor, the humidity sensor being mounted in the housing,
with the humidity sensor positioned in the housing lower than the control
processor, the power circuits and the power line communication
reception/transmission system so as to sense ambient air humidity while
minimizing error introduced from heat generated by the control processor,
the power circuits and the power line communication
reception/transmission system.

17. The power line communicating programmable thermostat of claim 15,
further comprising:an occupancy sensor providing a sensed occupant result
to the control processor, wherein the programmable thermostat transmits
occupancy information using the power line communication
reception/transmission system.

18. The power line communicating programmable thermostat of claim 15,
wherein the programmable thermostat transmits sensed temperature
information using the power line communication reception/transmission
system.

19. The power line communicating programmable thermostat of claim 15,
wherein the programmable thermostat transmits temperature set point
information using the power line communication reception/transmission
system.

20. The power line communicating programmable thermostat of claim 15,
wherein the housing comprises a heat channeling separation wall above the
temperature sensor and below the control processor, the power circuits
and the power line communication reception/transmission system.

[0002]The present invention relates to programmable thermostats, and, more
particularly, to programmable thermostats and thermostat systems used in
heating, ventilation and air conditioning ("HVAC") systems for buildings
which can communicate with a utility such as through using a power line
communication (also known as power line carrier, hereinafter referred to
as "PLC") signal.

[0003]Increases in efficiency in utilizing energy are continuously needed,
and are becoming even more important with our country's movement off of
foreign-provided fossil fuels and into alternative and cleaner energy
sources. One of the primary ways in which we use energy is in heating,
cooling and ventilating our indoor spaces. Sometimes fossil fuels, such
as natural gas, are delivered to a building for use such as in heating
the indoor spaces. Other times, energy is delivered to the building using
electricity; the actual source of the energy for the electricity might be
a fossil fuel, but more frequently is becoming a renewable, cleaner
source, such as hydroelectric, wind or solar. In either event, the
utility provider of the energy often has an incentive to control the rate
of energy use which competes with the desires or strategy of the building
occupant.

[0004]For instance, on a hot day a building resident may wish to maximize
air conditioning use to keep the indoor space as cool as possible. Air
conditioners represent significant consumption of electricity. When many
building occupants in a geographic area behave similarly in this regard,
the peak electricity load on a hot day may be several times the average
electricity load handled by a utility company. The utility's
systems--indeed the entire national electronic grid--must handle
significant differences in electrical loads, which adds tremendous cost.
As we move toward alternative energy sources, these differences in
electrical loads can be magnified, such as when the hot (increased air
conditioning) weather is also still and dry (resulting in decreased
supply of wind and hydroelectric power).

[0005]One conceptual strategy to reduce such costs is for the utility
company to more directly influence the level of energy consumption. Some
utility companies have changed pricing structures, such as charging
higher prices for electricity at times of peak demand. Other utility
companies have offered reduced overall pricing to consumers who will
allow the utility company to curtail their energy usage at times of peak
demand. Regardless of the mechanism used, the effective implementation of
such a strategy presents many thorny problems. There are hundreds of
different utility companies, each of which will likely want to implement
slightly different strategies, and millions of different consumers having
different desired responses to whatever strategy is implemented by their
utility company. There are numerous pieces of equipment, made by numerous
different entities, involved between the utility company and the
consumer.

[0006]In an effort to come to some standardization and provide a means of
addressing these problems, groups such as the California Energy
Commission have set up a task force called UtilityAMI for the development
of high-level guidelines and open standards for advanced metering options
within a home area network. See the UtilityAMI 2008 Home Area Network
System Requirements Specification provided at
http://osgug.ucaiug.org/sgsystems/openhan/Shared%20Documents/UtilityAMI%2-
0HAN%20SRS%20-%20v1.04%20-%2008 0819-1.pdf, incorporated by reference. See
also U.S. Pat. No. 7,702,424, incorporated by reference. While these
communication guidelines provide some level of help in allowing utility
companies and HVAC equipment manufacturers to build systems which will
facilitate communication, much implementation work is left to be done.

[0007]For instance, even if an open source language is adopted, there are
various modes of communication which can exist between pieces of HVAC
equipment. One possible mode of communication for the utility company is
to communicate instructions over a PLC signal, i.e, to embed the
instructions in a radio frequency ("RF") signal transmitted over the same
power lines which transmit the electricity. Devices for the generation,
transmission, reception and decoding of such PLC signals are commercially
provided by companies such as Bel Fuse Inc. of Jersey City, N.J. under
the HOMEPLUG designation. However, the vast majority of PLC devices
involve communication between a transmitter and a receiver both located
within a building and made by the same company, rather than between a
transmitter or receiver located a significant distance away from the
building communicating with another manufacturer's device. The utility
company will thus have many decisions and implementation issues to
effectively generate and transmit instructions to each building where the
utility seeks to influence the level of energy consumption.

[0008]To the extent that PLC signals have been contemplated for signal
generation by the utility company for use within a building, HVAC
equipment manufactures have generally pursued receiving a PLC signal at
the electricity meter, at a main electrical junction box or at similar
location for the building, and then wirelessly transmitting (such as
using a ZIGBEE transmission) a related set of instructions to various
pieces of equipment installed within the building. However, wireless
communication presents its own set of difficulties, not the least of
which is a limited distance of transmission under current FCC standards.
Other systems which have considered use of a PLC signal, such as U.S.
Pat. No. 4,241,345, have not specifically considered how the PLC signal
would be propagated and received. Better and more cost effective systems
are needed.

BRIEF SUMMARY OF THE INVENTION

[0009]The present invention involves a utility demand response/home
automation network (HAN)-standard programmable communicating thermostat,
and a system utilising the programmable communicating thermostat. The
thermostat receives information from a utility using a power carrier line
signal using the distributed low voltage power lines downstream of an
HVAC system transformer, and transmits information to the utility using
the same distributed low voltage power lines. In one aspect, the HVAC
system transformer includes an integral capacitive bypass path for PLC
data transmission across the windings of the transformer. In another
aspect, the thermostat positions its temperature sensor to avoid heat
given off by the PLC receiver/transmitter and its electrical circuits as
well as the microprocessor and the electrical power circuits therefore.
The two-way PLC communication includes transmission to the utility of
response information regarding the response taken by the thermostat to a
power "shed" command, and preferably also includes sensed temperature
and/or temperature set point information.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a schematic depiction of the use of the present invention
relative to a building.

[0011]FIG. 2 is a partial schematic of the transformer and partial back
view schematic of the programmable communicating thermostat of the
present invention.

[0012]FIG. 3 is a simplified back view of the circuit board layout for the
programmable communicating thermostat of the present invention.

[0013]While the above-identified drawing figures set forth a preferred
embodiment, other embodiments of the present invention are also
contemplated, some of which are noted in the discussion. In all cases,
this disclosure presents the illustrated embodiments of the present
invention by way of representation and not limitation. Numerous other
minor modifications and embodiments can be devised by those skilled in
the art which fall within the scope and spirit of the principles of this
invention.

DETAILED DESCRIPTION

[0014]As shown in FIG. 1, the present invention involves a system in which
a utility company 10 is providing energy, typically electricity, to a
building 12. The building 12 uses the energy provided for various
purposes, including running the heating, ventilation and air conditioning
("HVAC") system 14 for the building 12. The HVAC system 14 includes known
components of common HVAC systems, depicted in this case as a "central"
air system 16 with an exterior air conditioner compressor/condenser unit
18 with refrigerant lines 20 running to an interior air conditioner
evaporator/fan 22.

[0015]The air conditioner 16 is controlled by a thermostat unit 24 which
includes a temperature sensor 26 to measure the temperature of air within
the building 12. As typical of advanced thermostats, the thermostat 24
includes a display 28 and controls 86 to enable a building occupant to,
among other functions, change the set point temperature for operation of
the air conditioner 16. The thermostat 24 is located within the building
12 at a location convenient for the resident, such as on a wall centered
on the main floor of the building 12, where the sensed temperature will
also be representative of an average air temperature for the building 12.
In prior art respects, the design of the thermostat 24 of the present
invention is taken from that of the FLEXSTAT programmable thermostat of
KMC Controls, Inc. of New Paris, Ind., assignee of the present invention.

[0016]Primary power for the building 12 is distributed throughout the
building 12 in a standard manner, in the U.S. typically as a 120 V
alternating current (60 Hz) system 30. The power consumption of the
building 12 is metered by the utility company 10 with an electricity
meter 32, which meter readings are used to bill the consumer for the
amount of energy used. The electricity meter 32 is typically located on
or near the outside of the building 12 and near a main electrical control
panel or circuit breaker box (not separately shown). Typically the
utility company 10 will provide similar power to numerous buildings in a
geographic area.

[0017]While primary power for the building 12 is provided at 120V AC, the
thermostat 24 typically is driven with a different, lower voltage power
supply, such as a "Class 2" 24V AC supply. The 24V AC supply is generated
by an HVAC system transformer 34 having a primary winding 36 and a
secondary winding 38 which cooperate to lower the primary 120 V AC
electricity to the desired 24V AC supply for the HVAC system 14. Often
the transformer 34 is located a significant or "distributed" distance
within the building 12 away from the thermostat 24; i.e., at a location
wherein the 24V AC line 40 is run through the walls of the building 12.
In some buildings the transformer may be located in a mechanical room
where the primary air handling equipment (furnace, fans, etc.) is
located, in other buildings the transformer may be located adjacent or in
the main electrical control panel for the building.

[0018]While the occupant has primary control over the thermostat 24, the
utility company 10 desires to charge the occupant at different rates or
otherwise exert some influence over the amount of energy used by the
building 12, particularly for lowering the amount of energy used by a
collection of buildings during peak consumption or during a power
shortage due to exterior, low-power-generation, conditions. For utilities
which charge at different rates, the most common solutions involve a
"smart meter" which communicates to the utility the amount of electricity
used during shorter time periods consistent with rate changes.

[0019]However, schemes for the utility company 10 to influence the amount
of energy consumed can be made more effective by utilizing information
not just known by the meter 32, but also information known within the
thermostat 24. Examples of such thermostat-known information are the set
point temperature to activate the air conditioner 16 and the sensed air
temperature, both of which are not generally known to the utility 10 or
to the meter 32. Schemes for the consumer to adjust the amount of energy
consumed can be made more effective by utilising real time knowledge of
the pricing structure of the utility company 10, which may or may not be
known within the meter 32 and is not commonly considered or known in most
basic thermostat control systems.

[0020]The present invention particularly contemplates two-way
communication with the utility company 10 and the thermostat 24. The
present invention provides a method and device for communicating
information between the thermostat 24 and the utility company 10 to
effectuate more efficient and controlled use of energy within the
building 12. The inventive system enables the consumer to exert flexible,
set-and-forget control over the HVAC energy use without the expense of a
large building automation system, while providing the utility 10 with
more influence over the amount of HVAC energy use during peak usage time
periods.

[0021]A first important aspect of the system is to transfer the 120V AC
PLC signal to the thermostat 24. While such transfer seems simple in
concept, in practice both the electrical systems of most utility
companies and the electrical system within the building 12 introduce a
significant amount of radio frequency noise onto the 120V AC power line
30 (only partially shown). The amount of RF noise is not so great as to
defeat most PLC applications when the RF signal is generated close (i.e,
within the same building) to the receiver, but becomes worse when the RF
signal is generated by the utility company 10 outside the building 12.

[0022]More significantly, step-down transformers (not shown) are used to
reduce the voltage transmitted by the utility company 10 down to the
voltage for use by customers. PLC signals cannot readily pass through
transformers, as the high inductance of the transformers makes them act
as low-pass filters, substantially blocking RF signals. One way around
this problem is to attach a signal repeater across each transformer. See,
for instance, U.S. Pat. Nos. 7,675,408 and 7,414,518, incorporated by
reference. Regardless, the present invention considers that the system
used to transfer the PLC signal from the utility's transmission voltage
down to the building operating voltage (typically 120 Volts, starting at
least at either the meter 32 or the main electrical box) is within the
control and province of the utility company 10.

[0023]Rather than using a repeater, the more common solution in the HVAC
industry is to wirelessly transmit the PLC commands to the thermostat 24.
However, the present invention avoids wireless transmission and reception
(at least upstream of the thermostat 24) and the expense and problems
inherent in such wireless transmission of the original PLC information.

[0024]A key feature of this system is thus that the thermostat 24
communicates with the utility company 10 through the class 2 wiring 40,
HVAC system transformer 34, and 120V AC line 30 without additional in
home wiring. In one aspect, the present invention involves the use of a
capacitor 44 within the HVAC system transformer 34 to transfer the PLC
signal to the thermostat 24 using the class 2 24V AC power line 40. The
capacitor 44 is electrically connected across the primary winding 36 and
secondary winding 38 of the HVAC system transformer 34. For instance, a
120V AC primary, 24V AC secondary transformer from Stancor Products
(division of Emerson Electronics, St. Louis, Mo.) can be modified by
adding the capacitor 44 across the primary winding 36 and secondary
winding 38. Alternatively and more preferably for a commercial
embodiment, the capacitor 44 can be added within the same housing as the
windings 36, 38 of the transformer 34. The commercial embodiment of the
HVAC system transformer 34 could alternatively be rated for 240V AC on
the primary side. The capacitor 44 assists in analog transference (i.e.,
without any interpretation of the signal contents) of the PLC RF signal
across the transformer 34. The integral capacitive bypass path for data
transmission is particularly important when retrofitting older
inexpensive HVAC systems or in applications where significant electrical
noise may be present such as multi-family dwelling units.

[0025]Another significant aspect of the present invention is that the
thermostat 24 communicates back to the utility 10 utilising the same 24V
AC power line 40. The use of a capacitor 44 is important in the respect
that the present invention contemplates transferring PLC signals in both
directions, i.e., from the utility 10 to the thermostat 24 and from the
thermostat 24 to the utility 10. This communication back to the utility
10 needs to occur within real time (i.e., a period measured in seconds,
such as preferably less than 60 seconds and in no event more than 300
seconds) so that the utility 10 has near real-time feedback information
for use in closed loop control of demand control strategies over a wide
geographic area when many of these thermostats 24 are deployed. The
preferred thermostat 24 communicates back to the utility 10 within about
3 seconds of responding to a utility "shed" condition.

[0026]Another advantage of using the capacitive bypass HVAC system
transformer 34 is that the transformer 34 can be installed without
requiring a licensed electrician to do the work. The capacitive bypass
HVAC system transformer 34 may be easily and quickly installed in HVAC
systems either at the factory by the original equipment manufacturer or
in existing residential applications through a simple retrofit procedure.

[0027]The use of a capacitor 44 is important in another respect in that
the primary winding 36 of the transformer 34 is typically only at 120V
AC. Should the capacitor 44 short, the supply voltage provided to the
thermostat 24 will still only be at 120V AC which can minimize the
dangerous fire hazard situation which could occur if the primary winding
36 was at a higher voltage. Alternatively, one or more fuses (not shown)
can be added to avoid conducting current should the capacitor 44 short;
because the transformer 34 is dedicated to the 24V HVAC system line 40
for the thermostat 24, tripping the fuse does not disrupt the power
supply for the rest of the building 12.

[0028]The present invention uses a high quality capacitor 44 with a low
effective series resistance rated for a voltage significantly higher than
the voltage on the primary winding 36, such as rated at 250V or higher
when used with a 120V AC primary voltage. The capacitor 44 should have a
capacitance between 50 and 10000 pico farads, and preferably a
capacitance of 500 to 1000 pico farads. The high quality capacitor 44 is
much less expensive than using either a two-way repeater or a wireless
transmitter/receiver within the HVAC system transformer 34.

[0029]The 24V AC PLC signal can be received at the thermostat 24 and
processed using commercially available components. In the preferred
embodiment, a Bel Fuse HOMEPLUG Low Power SIMPLE Embedded Power Packet
Module 46 is used to receive and send the PLC signal. The PLC module 46
connects into the primary circuit board 48 with a 40 pin connector 50.
The PLC module 46 is capable of Internet Protocol communication data
rates in excess of 1 Mbps utilising industry standard Ethernet frame
conventions and messaging. The power signals and reception/transmission
pairs for the PLC module 46 are routed using matched trace lengths. The
PLC module 46 receives the 24V AC line 40 through an input 52 on the
circuit board 48, which is then directed through a PLC conditioning
circuit 54 to the PLC module 46 while separating power for the power
circuits 56 of the thermostat 24. In the preferred embodiment, the PLC
conditioning circuit 54 includes a 47000 pico farad capacitor 58 in
parallel with a series of two 200 KOhm resistors 60, which is then
directed through a 0557-7700-04 powerline signal coupler 62 from Bel Fuse
of Jersey City, N.J.

[0030]The power circuits 56 on the thermostat 24 are used to reduce the
incoming 24V AC supply to regulated power supplies on the circuit board
48. In the preferred embodiment this includes three regulated supplies.
The power input is first is directed across a transient voltage
suppressor 64 through two ELJPA220KF 22 micro-henry chip inductors 66
from Panasonic, and then to power circuits 56 identified on the circuit
board 48 as REG3, REG2 and REG1. In REG3, the primary component 68 is a
LM25575 step down switching regulator from National Semiconductor,
generating VDD of 15 V. In REG2, the primary component 70 is a
LM2734 PWM step down DC-DC regulator from National Semiconductor,
generating VCC of 3.3 V. In REG1, the primary component 72 is an
Ultralow-Noise, High-PSRR, Fast, RF, 250-mA Low-Dropout TPS70401 Linear
Regulator from Texas Instruments of Dallas, Tex., generating VCORE
of 1.8 V.

[0031]The PLC signal on the incoming 24V AC power line 40 causes the power
circuits 56 and the powerline signal coupler 62 to generate heat which,
unless otherwise adjusted for, can be sensed by the temperature sensor
26. As best shown in FIGS. 2 and 3, the power circuits 56 of the
transmitter are located on the top of the circuit board 48, above the
main microprocessor 74. The powerline signal coupler 62 is located
relatively high on the circuit board 48 but beneath the power circuits
56. At the same time, the temperature sensor 26, and the optional
humidity sensor 76 and occupancy sensor 78, are located on the bottom of
the circuit board 48. This layout helps avoid misreadings because the
heat rises from the power circuits 56 and powerline signal coupler 62
away from the temperature sensor 26 and optional humidity sensor 76.

[0032]A heat channeling separation wall 80 is located in the housing 81 of
the thermostat 24. Vents 82 are provided in the lower and upper walls of
the housing 81. The vents 82 and separation wall 80 direct heat generated
by the electronics to ambient air, away from the on-board room
temperature sensor 26 and optional humidity and occupancy sensors 76, 78.
The use of this embedded thermal venting channel increases the accuracy
of the sensing elements 26, 76, 78, allowing closer control of the
affected spaces. The preferred housing 81 is about 4 inches wide, 51/2
inches tall and 11/2 inches deep, with the separation wall 80 extending
about three fourths of the way across the housing 81 from left to right
as view from the front (FIGS. 2 and 3 are rear views). The preferred
vents 82 are about 24 holes of about 1/4 inch diameter in the top and
bottom walls of the housing 81.

[0033]A user interface 84 on the front face of the thermostat 24 allows
the user to read and set various functions within the control program.
The preferred user interface 84 and standard thermostat control program
are similar to those of the FLEXSTAT programmable thermostat of KMC
Controls, Inc. of New Paris, Ind., assignee of the present invention. In
particular, the preferred input mechanism 86 utilizes a five button
control. This input mechanism 86 not only allows configuration of
standard thermostat functions (such as temperature set point), but also
allows configuration of which HVAC actions will take place in which order
in response to the various commands or data provided by the utility 10.
The user interface 84 also includes a high-contrast backlit dot matrix
LCD display 28 (68×128 pixel) similar to the FLEXSTAT programmable
thermostat 24. The control program is stored on one or more memory chips
88, 90 and carried out on a primary microprocessor 74 chip for the
thermostat 24. The preferred embodiment uses a MCF5274L microprocessor 74
from Freescale Semiconductor of Austin, Tex., in conjunction with two 32
MB flash memory chips 88 and an 8 MB SRAM chip 90. Other standard
circuits, such as clock circuits, watchdog circuits, EEPROM circuits,
debugging circuits, power back up circuits, etc. (not separately called
out) can also be included on the circuit board 48.

[0034]As known in the programmable thermostat art, the thermostat 24 can
optionally include additional inputs 92 for use by the control program
and additional outputs 94 operated by the control program. Relays 96 for
the outputs 94 are used to automatically turn on or off other connected
loads in response to a pre-programmed, but configurable "demand response"
or "power shedding" program. Common applications for the additional
outputs 94 are the retrofit of existing pneumatic VAV terminals, fan coil
units, and water source heat pumps in buildings where power is already
present at the controlled terminal unit, but digital controls were not
used during the initial installation. Typically the inputs 92 receive
0-12V analog signals, but other settings for the inputs 92 could be used.
Typically the outputs 94 can provide analog signals 0-12V, maximum 20 mA
or digital signals through the relays 96 of 1 A per relay 96, 1.5 A total
for banks of three relays 96 at 24 VAC/VDC, but other settings for the
outputs 94 could alternatively be provided.

[0035]In the preferred embodiment, the user interface 84 allows access to
and display of a menu driven control program permitting entry of
instructions and display of data. In particular, the data and settings in
the control program include but are not limited to: [0036]a. Normal
permissible daily operating schedules and temperature setpoints for
connected HVAC equipment. The thermostatic functions may be programmed by
the owner to automatically set up and setback operating HVAC setpoints
during the day as is commonplace with residential programmable
thermostats, which may include scheduled "occupied" and "unoccupied"
modes, and scheduled daytime and nighttime modes. [0037]b. When the
thermostat 24 is provided with the optional occupancy sensor 78, the
control program adaptively learns the occupancy schedule of the connected
space and automatically reduces energy consumption of connected loads in
the HVAC system 14 accordingly. [0038]c. Display of current energy usage
conditions of the connected HVAC equipment, such as current Kw and KWH
consumed. [0039]d. Command status "event" information transmitted and
received from the utility company 10, such as "normal" operation, "alert"
status for a pending demand response event, and one or more indications
of a "shed" status of the various utility thresholds. [0040]e. Projected
current cost of operation during the event in currency/hour rate
measurements, based upon the event status and the current energy usage
information, as well as accumulated cost data. [0041]f. Operating
conditions of any other connected energy management loads controlled by
the thermostat 24 (such as On/Off control of other loads such as
televisions 100, lights 102, pool pumps (not shown), electric hot water
heaters (not shown), dryers (not shown), etc.) via the "relay" type
outputs 94 or via instructions transmitted from the PLC module 46.The
thermostat 24 provides rapid system response (typically less than 3
seconds) to a command from the utility 10 for near "real-time" display
and update of connected load and utility data information.

[0042]The thermostat 24 can transmit thermostat information to the utility
10, such as sensed temperature and temperature set point. The thermostat
24 also transmits a response to the utility 10 of actions taken in order
to let the utility grid control system get closed loop feedback for
management of overall grid electrical loads in a wide geographic area
when many of these systems are deployed on a large scale. In the
preferred embodiment, both the utility PLC information and the thermostat
PLC information are sent in conformance with UtilityAMI standards.

[0043]With the utility event status information received at the thermostat
24 and the thermostat information received at the utility 10, the present
invention allows control strategies that are not available in simple
smart meter installations, even if such smart meters are programmable.
The thermostat 24 allows adjusting heating and cooling setpoints of the
HVAC system 14 to immediately turn off the connected compressor, heating,
and fan loads while providing a minimum level of comfort and/or safety
protection by only allowing the temperature to "float" within specified
minimum and maximum values. For instance, during a "shed" event, the
sensed temperature of indoor spaces can be used in establishing the
control strategy, such as with the system allowing full HVAC power to
spaces having a temperature of greater than 82° F., or with a
sensed temperature/set point differential of greater than 5° F.

[0044]The utility company 10 and/or the user can establish numerous
different complex "shed" protocols, such as shed protocols based upon the
temperature and/or humidity differential between exterior conditions and
interior conditions at each residence. If occupancy information is
transmitted, the utility's "shed" strategy can be directed more to
unoccupied spaces. The utility company 10 can also make a real time
estimate the amount of load reduction which will be obtained which each
different "shed" strategy, to better decide which "shed" strategy to
pursue for each peak demand event. The feedback annunciation of control
actions within the building 12 to the utility 10 enables the utility 10
to improve its forecasting strategy for each different type of demand
event, enabling the utility 10 to fine tune its various array of "shed"
strategies based upon real-time building-specific information. The real
costs of the utility company 10 can be more directly and equitably bourn
by the various utility customers, and power used more efficiently by the
entire system.

[0045]In addition to the outputs 96 directly controlled by the thermostat
24, the thermostat 24 optionally may be used to communicate with other
devices on the building's 120V AC power lines 30, if such other devices
are similarly configured with PLC receivers. For instance, other
electricity consuming devices such as a television 100, electric clothes
dryer or dishwasher (not shown) may have a PLC receiver configured to
receive a signal generated by the thermostat 24 and transmitted through
the 24V AC power line 40 and HVAC system transformer 34. Then the control
program may turn off various loads throughout the building 12 as selected
by the resident in response to the rising price of electricity and/or
status signals sent by utility 10, such as [0046]a. In response to a
first "shed" condition signal from the utility 10, turn off a connected
swimming pool circulating pump (not shown) via a commanded relay output,
and adjust HVAC setpoints in unoccupied spaces. [0047]b. In response to a
second "shed" condition signal from the utility 10, adjust HVAC setpoints
in occupied spaces. [0048]c. In response to a third "shed" condition
signal from the utility 10, reduce other appliance loads such as
commanding a TV 100 into standby mode via an addressable wall socket,
[0049]d. In response to a fourth "shed" condition signal from the utility
10, turn off lights 102 depending on the time of day, or turn off an
electric hot water heater (not shown) depending on the time of day and
outside temperature, via a commanded relay. [0050]e. In response to a
fifth "shed" condition signal from the utility 10, command a running
electric dryer or dishwasher (not shown) to complete their operating
heating cycle and then go to a "safe" operating mode as determined by the
appliance manufacturer by sending a command to the addressable
microcomputer located in the device.

[0051]Of course, the thermostat 24 also operates in a "normal" mode for
the user to control the energy usage within the home during standard
operating conditions that occur when the utility 10 is not in a "shed"
command mode. In the "normal" mode, the scheduling functions of the
control program are extended to the outputs and to any other connected
electrical loads throughout the home via the addressable PLC capability,
enabling the user to schedule electrical energy usage during either
"off-peak" electrical rate periods, "time of day" periods, while the
occupancy sensor 78 determines that no one is present, or any combination
thereof. In addition, the scheduling functions are extended to other
connected electrical loads throughout the home via the addressable device
capability or other directly connected loads to schedule electrical
energy usage during either "off-peak" electrical rate periods, while the
homeowners may or may not be present, or both. This capability further
allows the user to use the thermostat control program to minimize
consumer energy costs.

[0052]If desired, the thermostat 24 may have other communication
structures which allow the control program to be set in ways in addition
to the user interface 84. For instance, the preferred thermostat 24 has a
RS 485 chip 98 and connection (not shown, provided on bottom wall of
housing) permitting a computer connection directly to the thermostat 24
via an RS 485 cable. As another additional optional example, the
thermostat 24 may transmit on the 24V AC line 40 through the HVAC system
transformer 34, to be read by a commercially available
powerline-to-Ethernet transceiver (not shown) plugged into a wall socket
in the building 12 and then to a commercially available Ethernet hub,
switch, or router (not shown). As a third additional optional example,
the thermostat 24 may include an Ethernet "RJ-45" connection (not shown)
that allows a conventional Ethernet cable to connect from the wall
controller location to a computer or to a commercially available Ethernet
hub, switch, or router device (not shown). As a fourth additional
optional example, the thermostat 24 may have an Ethernet speed (>1
Mbps) capable 2-way radio transceiver (not shown) that provides 2-way
wireless communication from the thermostat 24 to a wirelessly
transmitting computer in the vicinity.

[0053]With any one or more of these additional communication structures,
the thermostat microprocessor 74 and memory chips 88, 90 contains and
operates an embedded HTML web service with graphical display application.
The web service function serves up graphically displayed web pages to
provide viewing via an internet browser such as Internet Explorer or
Firefox. If communicating over the internet, access to the control
program is password protected. The user has 2-way data exchange with
these web pages and may use them to view current operating conditions on
the webpage, to override utility demand response commands, and to change
normal operational conditions such as setpoints, schedules, and demand
response priorities. The web pages also graphically display energy use
information for the user in a formatted, easy to use manner.

[0054]The complete integrated residential home energy management system
consists of the thermostat 24 and its resident software, firmware,
application control sequences and algorithms, the HVAC system transformer
34, connected HVAC electricity-consuming components 16, and other
electricity-consuming loads within a typical building 12. The invention
specifically provides control of the energy usage within the home in
response to 2-way utility command and control signals and messages found
within the "Smart Grid" environment of modern electrical utilities to
help utilities manage system electrical demand across a wide geographic
area. The system embodies a complete process of operating in a variety of
normal and electricity "shed" modes to minimize the energy usage within
the building 12.

[0055]Although the present invention has been described with reference to
preferred embodiments, workers skilled in the art will recognize that
changes may be made in form and detail without departing from the spirit
and scope of the invention.